It's been more than ten years since Dr. Ferdinand Piëch started playing around with the idea of a car that asks for only 1-liter of fuel in exchange for 62 miles of travel. A decade on, the XL1 is production ready. Here is how it works.

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Let's start with the engine. It's a 0.8-litre TDI which they made by cutting the 1.6 TDI in half. There are specially formed piston recesses for multiple injection and individual orientation of the injection jet, while the high-precision aluminum crankcase and the balancer shaft (that is driven by the crankshaft turning at the same speed) makes sure the 0.8 runs just as smoothly as its larger brother. The result is 47 horsepower and 89 foot pounds of torque.

Since the car weighs only 1741 pounds, this tiny diesel would be enough for most situations, but the Germans went further by adding a 27 horsepower electric motor installed to the TDI in the rear section of the car. The 5.5 kWh lithium battery went to the front. This whole drive unit weighs only 500 pounds, and is linked to a seven-speed DSG for efficiency. While in all electric mode, the XL1 promises up to 31 miles of range, the combined power of the TDI and the electric boost function gives the car 68 horsepower and 103 ft-lb. That means a 0-62 in 12.7 seconds, and a top speed limited to 100 mph. It also means incredibly low fuel consumption.

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It's not just the drive unit that got lighter thanks to some clever engineering. The running gear is only 337 pounds. In front, a double wishbone suspension is used, while a semi-trailing link system is employed at the rear, using aluminium suspension components, brake calipers, dampers and steering gear housing, as well as carbon fiber anti-roll bars, ceramic brake discs, magnesium wheels and plastics for the steering wheel body. Electronics are 176 lb, equipment is 231, which leaves 507 pounds for body made entirely of carbon fiber.

The low weight and center of gravity together with a drag coefficient of Cd 0.189 and low resistance Michelins mean that the XL1 needs only 8.4 horsepower to cruise at a constant 62 mph. This optimized body shape results in a slightly offset side-by-side seating, while wing doors were used which are hinged at two points: low on the A-pillars and just above the windscreen in the roof frame, so they do not just swivel upwards, but slightly forwards as well. The XL1 is 3,888 mm long, 1,665 mm wide and just 1,153 mm tall, but Volkswagen helps with the translation: "Shorter than a Polo, lower than a Porsche Boxster".

Looking at the rear, Tatra says hi! Another interesting detail is that the the air conditioner is installed on the outside in a capsule in the car’s front section, simply because there wasn't any space elsewhere. There is some for luggage though, as the XL1's trunk can take 4.23 cubic feet of stuff.

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Production of the XL1 will be pretty much made by hand in Osnabrück. The CFRP monocoque is produced by a supplier in Austria using the RTM process, which is the way carbon fiber components can be mass produced. The body is built without doors or lids, while individual CFRP components are joined to one another in the body shell frame by gluing. The two wing doors are produced in a separate production stage including their crash reinforcements, since high precision is needed as carbon elements cannot be reshaped afterwards.

After all the parts are in place, a total of 32 exterior skin parts are painted on the XL1. Despite a minimally thin paint layer, a special fleece layer or resin film is added to the carbon parts as a cover coat, which is still 50 percent lighter than what's normally used. In the interior, a matte grey paint is applied as well as a matt clear coat on visible carbon fiber.

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The shiny body then joins the prefabricated floor, complete with the suspension and the drive unit. Unlike in mass production, all individual cockpit parts are mounted inside the vehicle superstructure. The dashboard itself consists of a molded wood fibre material.

After assembly of the drive unit, the 0.125 inch thick windscreen is installed. The wing doors are reinstalled with their exact positions and alignments already set earlier. The XL1 gets its bonnet and magnesium wheels. But playing with the doors is not over. After installing the painted door and integrating the window mechanisms, special assembly fixtures are used to glue the polymer side windows into place. When the reversing cameras are placed in their housings, the XL1 is ready for its first startup.

This labor intensive engineering masterpiece sure sounds interesting, I just don't want to think about its price when it will finally hits the showrooms. In the long run though, it can save its buyers quite a sum.